Apparatus for fines recovery in carbon black-rubber masterbatch production



Oct. 9, 1962 R. s. HANMER APPARATUS RoR EINES RECOVERY IN CARBONBLACK-RUBBER MASTERBATCH PRODUCTION Original Filed Deo. 26, 1956 mmmUXmIN V EN TOR.

R S HANMER Y yfdy/ ATTORNEKS` United States Patent G 3,057,697 APPARATUSFR FINES RECOVERY IN CARBN BLACK-QUEBER MASTERBATCH PRODUCTION Robert S.Baumer, iiartlesviiie, Okla., assigner to Phillips Petroieurn Company, acorporation of Deiaware Original application Dee. 26, 1956, Ser. No.630,551, 110W Patent No. 2,979,481, dated Apr. 11, 1961. Divided andthis appiieation Sept. 19, 1960, Ser. No. 56,906

4 Claims. (Cl. 23--260) This invention relates to carbon black-rubbermasterbatch production. I-n a further aspect this invention relates tocarbon black-rubber masterbatch production wherein losses due to nes arereduced. In a further aspect this invention relates to apparatus forcarrying out this method.

This application is a division of my application Serial No. 630,551, ledDecember 26, 1956, now Patent No. 2,979,481, dated Apr. ll, 1961.

A problem exists in the production of such masterbatches in that aconsiderable amount of the product is lost as fines during itsproduction. Usual operation involves separating the coagulum from theseru-m, which may be returned to the coagulation zone, and then to washthe coagul-um with water, separate the water from the coagulurn andfurther process the coagulum. Fines are lost in the serum and in thewater from the subsequent washing operation. Losses of fines in theserum are small since this stream is usually returned to the coagulationzone except for Ithe small portion which is discarded as excess.

lllhe object of my invention is to provide apparatus for preparingcarbon black-rubber inasterbatch wherein losses due to lines areminimized.

Accompanying and forming a part of this specification is a drawingshowing, partly schematically, the apparatus of my invention.

A well-known practice in the rubber industry is to prepare rubber-carbonblack masterbatches by a latex masterbatching operation, -i.e., a carbonblack slurry is blended with la rubber latex and the mixture iscoagulated. An extender oil can also be added, if desired, and themixture coagulated to give a rubber-carbon black-extender oilcomposition. In the usual procedure, the mixture of rubber latex andcarbon black is first passed to a coagulation tank where a coagulantsuch as brine-acid is added and it is then transferred to a soapconversion zone where suiiicient time is allowed for conversion of thesoap to acid. Obviously, other coagulation systems can be used. Themixture is transferred to a shaker screen where rubber cru-mb containingcarbon black is separated from the serum. The serum which contains somefines, excess acid, and salt, is usually recycled to the acid-saltmake-up stream to the coagulation tank. An outlet is provided in therecycle -line for bleeding off excess liquid. Rubber crumb from theshaker screen is passed to a zone where it is Water washed. It is thentransferred to another shaker screen to effect separation of the crumbfrom the wash water and thence to further processing steps, such as tola hammer mill and a drier, while the wash water containing lines isdischarged as waste.

A much larger percentage of lines results from the washing operationthan from the first separation of rubber crumb from serum andconsiderable losses result when no provision is made for recovery of thefines. Filtration of the washed crumb is difficult on account of thetendency of the very fine particles to clog the shaker screen which isconstructed of the finest mesh material that is practicable in order tominimize the fines losses.

I have discovered that if the rubber crumb containing carbon black istransferred from the shaker screen to a perforated rolling belt and theserum or washed -water is sprayed or otherwise made to flow sevenly overthe layer of crumb on the belt, there is a substantial reduction infines losses. The rubber crumb provides a continuously renewed filtermedium through which the liquid containing the fines is passed. Byoperating in this manner, a substantial proportion of the lines isretained by the ru-bber crumb and losses are materially reduced. Theroller belt should be long enough to permit the crumb to drain to notover 40 and preferably not over 30 weight percent moisture after theliquid has filtered through it.

One .important advantage in operating according to the process of myinvention is that the shaker screen can be of coarser mesh than isordinarily employed thus yalleviating the plugging problem to a largeextent. The dact that a larger quantity of ne particle size rubber willpass through a coarser screen is of little consequence as it will beretained by the crumb on the roller belt as the serum is sprayed overit. Whereas screens of approximately mesh, say 90 -to 150 mesh have beenconsidered necessary, the use of my invention permits use of screens inthe range of 40` to 80 mesh.

My invention can probably be best understood by reference to theaccompanying drawing. In this drawing the principal pieces of apparatusused in carrying out my invent-ion comprise a coagulation tank =11, asoap conversion tank 121, a first shaker screen 13, a first perforatedconveyor belt 14, a water wash tank 16, a second shaker screen y17, asecond perforated conveyor belt 18, a hammer 1millf19, and a dryer 21.Coagulation tank l11 is provided with inlet condu-it 22 by means ofwhich a mixture of latex and carbon black `slurry is supplied to saidcoagulation tank. Coagulant is supplied through conduit 23. The efiuentfrom coagulation tank 1-1 is passed to soap conversion tank 12 by meansof conduit 24. From soap conversion tank 12. the mixture of carbonblack-rubber crumb and liquid is passed to shaker screen 13 by means ofconduit V2.6. The shaker screen is powered by motor 27. Solid materialconduit 28 is provided for conveying material from first shaker 113 toperforated conveyor belt 14 and conduit 29 is provided to convey solidmaterial from first shaker 13 to water Wash tank 16. Spray means 31, 32,33, and 34 are provided adjacent the upstream end of perfor-atedconveyor belt 14. Liquid passing through perforated conveyor belt 14 iscollected in tank 36 which is provided with outlet conduit 37, thisconduit extending to and communicating with coagulant supply conduit 23.A liquid removal conduit 38 having pump 39 therein extends from thelower portion of shaker 13. Conduit 41 extends from the :downstream endof conduit 38 to spray means 31 through 34, previously described.Conduit 42 connects conduit `38 with conduit 37. Extending from thebottom of wash tank 16 there is provided conduit 43 which communicateswith and extends to the upstream end portion of second shaker screen 17.Shaker screen 17 is powered by motor 44. Extending from shaker screen 17is conduit 46, this conduit conveying solid material to the upstream endof perforated conveyor belt 18. Conveyor belt 18 is provided with spraymeans 47, 48, 49, and 51. Extending from the lower end portion of shakerscreen 17 is liquid conduit 52, having pump 53 therein, conduit 52extending to spray -means 47 through 51. Liquid passing throughperforated conveyor belt 18 is collected in tank 54 and conveyed towaste by means of conduit 56.

Hammer mill 19 is provided at the downstream end of perforated conveyorbelt 18. Solid material from hammer mill 19 is conveyed to dryer 21 bymeans of conduit 57 and the product from dryer Z1 is recovered at lines58.

From this drawing the operation of my improved process should beevident. The mixture of latex and black slurry are coagulated incoagulation tank 11 by conventional means and passed to soap conversiontank 12 wherein the soap is converted to the acid. The coagulum ispassed to shaker screen 13 wherein it is separated from the serum. Atthis point, ralternative processes are possible within the scope of myinvention. In one method, the crumb is passed directly to wash tank 16by means of conduit 29 and the serum is passed by means of conduits 38,42, and 37 to the coagulation tank 11. A portion of the serum isdiscarded through conduit 59. Following washing of the coagulum withwater, the water and crumb is passed to shaker screen 17 by means ofconduit 43. Coagulum is passed from shaker screen 17 to perforatedconveyor belt 18 by means of conduit 46, being distributed on theconveyor belt by suitable means. The separated wash water containing aconsiderable amount of fines is passed by means of conduit 52 to spraymeans 47, 43, 49, and 51. This liquid containing the fines is sprayedupon the layer of rubber crumb and the major amount of the fines aredeposited upon and stick to the rubber crumb. The wash water,substantially free of fines, passes through the belt and collected intank 54 from which it is passed to waste or other use through conduit56. The crumb continues to pass along the perforated conveyor belt 1Sand drains to a moisture content preferably not above 30 or 4() weightpercent water. The crumb passes from the downstream end of conveyor belt18 to hammer mill 419 wherein it is disintegrated. It is passed to dryer21 by means of conduit 57 wherein a product of the desired moisturecontent is produced.

Alternatively, the crumb from shaker screen 13 can be distributed uponperforated conveyor belt 14 by means of supply conduit 28. In thismodification the serum recovered from shaker screen 13 is passed bymeans of conduits 38 and 41 to liquid spray means 31, 32, 33, and 34.Substantially all of the fines in this serum are deposited upon therubber crumb on perforated conveyor belt 14. The serum is collected intank 36 and passes by means of conduit 37 to the coagulation tank 11, asmall portion of this recycle serum being discarded through conduit 59.

From the downstream end of perforated conveyor belt 14 the rubber crumbpasses to water wash tank 16. In this modification it is also desirableto have a belt of sufficient length so that a considerable portion ofthe serum drains from the rubber crumb prior to its introduction intowash tank 16, this reducing the amount of wash water required.

The second modification just described provides the additional advantagein that fines are removed from the recycle serum and the fines are notlost in the small portion of material which is discarded. However, sincethe amount discarded is small, the additional equipment required forthis modification is sometimes considered unnecessary. Obviously, finesrecycled to the coagulation tank are not lost.

The following specific example is given as illustrative of the manner ofcarrying out the present invention and demonstrates the specificimprovement obtained thereby. However, it should be understood that ourinvention is not limited to this specific example.

Example Butadiene and styrene are copolymerized in aqueous emulsion at41 F. in accordance with the following recipe:

Parts by weight Butadiene 72 Styrene 28 Water 180 Rosin soap, K salt 4.5KOH 0.1 KCl 0.4

Cil

Parts by weight Tamol N1 0.1 Sequestrene AA2 0.02 FeSO4-7H2O 0.01NaSOCI-I2OI-I2I-I2O3 0.05 p-Menthane hydroperoxide 0.05 Tort-dodecylmercaptan 0.23

1Sodium salt of a. naphthnlene sulfonic acid-formaldehyde condensationproduct.

r`Ethylenediarnirle tetrnacctic acid.

3 Sodium formaldehyde sulfoxylate.

The reaction is shortstopped with 0.15 part Thiostop N (sodiumdimethyldithiocarbamate), based on monomers, and 1.5 parts by weight ofphenyl-beta-naphthylamine antioxidant is added per 10() parts rubber. Aconversion of 60 percent is reached in 15.2 hours. A polymer thusprepared has a Mooney value (ML-4) of approximately 58.

A carbon black slurry using high abrasion furnace black is prepared inaccordance with the following recipe:

Parts by weight Carbon black 50 lvlarasperse1 2 NaOH 0.2 Water 240 1Sodium lignin sulfonate.

The carbon black slurry is blended with the rubber latex in proportionssuch that 50 parts by weight of carbon black is employed per partsrubber. This latex masterbatch is fed to the coagulation tank wherebrine and acid are added and thence to the soap conversion zone whereconversion of the soap to acid occurs. The material is passed from thesoap conversion zone to a. shaker screen where the serum is separatedfrom the rubber crumb containing carbon black. Serum is recycled to thebrine-acid make-up line. Provision is made in the recycle line forwithdrawal of excess liquid as necessary. Rubber crumb from the shakerscreen is transferred to a washing tank where it is washed with water,passed to another shaker screen, and then to a perforated roller belt. Alayer of rubber crumb is formed on the belt. The wash water or serum ispumped through a transfer line to spray nozzles where it is spreadevenly over the surface of the rubber crumb. The crumb drains to amoisture content of not over 30 to 40 weight percent water and is thenpassed to a hammer mill and finally to a drier. The loss of rubber asfines is only 1.1 weight percent when operating in this manner.

When the run is repeated without provision for recovery of fines fromthe wash water from the second shaker screen, the loss of rubber asfines is 4.6 weight percent.

The emulsifiers which can be used include not only the soaps such asalkali metal or ammonium stearatcs, oleates, rosinates, and the like,but also alkali metal aralkyl sulfonates, aryl sulfonates, sodium ligninsulfonates, mercaptan ethylene oxide condensation products, phenolethylene oxide condensation products, etc. Mixtures of emulsifiers arefrequently used. As the emulsifier or mixture thereof is varied, itwill, in some instances, be necessary to vary the coagulation system.For instance, alcohols are used `as coagulation agents in some cases.

As many possible embodiments may be made from my invention withoutdeparting from the scope thereof, it is to be understood that all matterherein set forth is to be interpreted as illustrative and notas undulylimiting the invention.

I claim:

1. Apparatus for minimizing the loss of fines in the production ofcarbon black-rubber crumb comprising a coagulation tank, means to supplyrubber latex and carbon black slurry to said coagulation tank, a soapconversion tank, a conduit extending from said coagulation tank to saidsoap conversion tank, a first shaker screen, a conduit extending fromsaid soap conversion tank to said first shaker screen, means to recycleliquid from said first shaker screen to said coagulation tank, `a washchamber, means to convey crumb frrm said rst shaker screen to said Washchamber, a second shaker screen, means to convey material from said Washchamber to said second shaker screen, a perforated belt conveyor, meansto convey crumb from said second shaker screen .to one end portion ofsaid belt conveyor, spray means adjacent the end portion of said belt towhich crumb is supplied, means to convey liquid material from saidsecond shaker screen to said spray means, a hammer mill, means to conveycrumb from said belt to said hammer mill, a drier, and means to conveycrumb from said hammer mill to said drier.

2. Apparatus for minimizing the loss of fines in the production ofcarbon black-rubber crumb comprising a coagulation tank, means to supplyrubber latex and carbon black slurry to said coagulation tank, a soapconversion tank, a conduit extending from said coagulation tank to saidsoap conversion tank, a first shaker screen, a conduit extending fromsaid soap conversion tank to said rst shaker screen, a first perforatedbelt conveyor, means to convey crumb from said first shaker screen toone end portion of said first belt conveyor, first spray means adjacentthe end portion of said first belt conveyor to which crumb .is supplied,means to convey liquid from said first shaker screen to said rst spraymeans, means to convey liquid from said -rst belt conveyor to saidcoagulation tank, a Wash chamber, means to convey crumb from said firstperforated belt to said Wash chamber, a second shaker screen, means toconvey material from said Wash chamber to said second shaker screen, asecond perforated bel-t conveyor, means to convey crumb from said secondshaker screen to one end portion of said second perforated beltconveyor, second spray means adjacent the end portion of said secondbelt conveyor to which crumb is supplied, means to convey liquid fromsaid second shaker screen to said second spray means, a hammer mill,means to convey crumb from said second belt conveyor, to said hammermill, a drier, `and means to convey crumb from said hammer mill to saiddrier.

3. Apparatus for minimizing the loss of nes in the production of carbonblack-rubber crumb including a wash chamber, means to supply crumb tosaid Wash chamber, a shaker screen, liquid collection means below saidshaker screen adapted to collect liquid passing therethrough, means toconvey crumb from said wash chamber to said shaker screen, a perforatedbelt conveyor, means to convey crumb from said shaker screen to one endportion of said belt conveyor, spray means having 'a liquid supplyinlet, said spray means being adjacent the end portion of said belt towhich crumb is supplied, means to convey liquid material from saidliquid collection means directly to said liquid supply inlet of saidspray means, a drier and `means to convey crumb from said belt to saiddrier.

4. Apparatus for minimizing lthe loss of nes in the production of carbonblack-rubber crumb comprising a coagulation tank, means to supply rubberlatex and carbon black slurry to said coagulation tank, a soapconversion tank, a conduit extending from sai-d coagulation tank to saidsoap conversion tank, 'a first shaker screen, a conduit extending fromsaid soap conversion tank to said rst shaker screen, means to recycleliquid from said first shaker screen to said coagulation tank, a Washchamber, means to convey crumb from said first -shaker screen to saidWas-h chamber, a second shaker screen, means to convey material fromsaid Wash chamber to said second shaker screen, a perforated beltconveyor, means to convey crumb from said second shaker yscreen to oneend portion of said belt conveyor, spray means adjacent the end portionof said belt to which crumb is supplied, means to convey liquid materialfrom said second shaker screen to said spray means, a drier, and meansto convey crumb from said belt to said drier.

References Cited in the tile of this patent UNITED STATES PATENTS2,545,144 Green et al Mar. 13, 1951

1. APPARATUS FOR MINIMIZING THE LOSS OF FINES IN THE PRODUCTION OFCARBON BLACK-RUBBER CRUMB COMPRISING A COAGULATION TANK, MEANS TO SUPPLYRUBBER LATEX AND CARBON BLACK SLURRY TO SAID COAGULATION TANK, A SOAPCONVERSION TANK, A CONDUIT EXTENDING FROM SAID COAGULATION TANK TO SAIDSOAP CONVERSION TANK, A FIRST HAKER SCREEN, A CONDUIT EXTENDING FROMSAID SOAP CONVERSION TANK TO SAID FIRST SHAKER SCREEN, MEANS TO RECYCLELIQUID FROM SAID FIRST SHAKER SCREEN TO SAID COAGULATION TANK, A WASHCHAMBER, MEANS TO CONVEY CRUMB FROM SAID FIRST SHAKER SCREEN TO SAIDWASH CHAMBER, A SECOND SHAKER SCREEN, MEANS TO CONVEY MATERIAL FROM SAIDWASH CHAMBER TO SAID SECOND SHAKER SCREEN, A PERFORATED BELT CONVEYOR,MEANS TO CON-